Catalytically sweetening heating oils



Nov. 22, 1955 s. B. swEETsER .ETAL 2,724,584

CATALYTICALLY SWEETENING HEATING OILS Filed NOV. 20, "1952 V o? r C I 8 T O'V L.

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'-r z Q Oxa-VILLA 'ZONE "Wl O' Stan?, .Ear fzs En nl; s JRobermcowbl Ve or United States Patent() 1 2,724,684 CATALYTICALLY SWEETENING HEATING OILS Sumner B. Sweetser, Cranford, Stanley 0. Bronson II, Mountainside, and Robert C. Morbeck, Fanwood, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application November 20, 1952, Serial No. 321,652 i 4 Claims. (Cl. 196--t-28) The present invention is concerned with an improved p process for the production of high quality heating oils.

` heating oils, of the nature employed in various burner systems, as diesel fuels, or as domestic and industrial heating oils. Heating oils may be derived from petroleum 2,724,684 Patented Nov. `22,` 11955 On 'the other hand, light cracked heating oils in many operations merely require a caustic wash. However, the

conventional procedure is to secure the cracked heating oil from a relatively severe cracking operation in which case it is necessary to acid treat the cracked heating oil followed by a caustic wash in order to control the'carbon residue. This latter operation is not desirable since acid treatment polymerizes many desirable constituents which have to be removed by an expensive rerunning opera-` tion resulting in a loss in yield. Furthermore, the sludge is expensive and dilicult to handle.

In accordance with the present invention, linished heating oils of a satisfactory carbon residue content are produced by blending catalytically sweetened virgin heating oil constituents with cracked heating oil constituents which preferably have been caustic washed.` This process eliminates the further treatment of the cracked stocks that would otherwise be necessary due` to the serious carbon residue incompatibiltiy tha't occurs whenblending conversion sweetened virgin heating oil constituents with cracked heating oil constituents.`

by a variety of methods including straight distillation` from crude petroleum oil, and thermal or catalytic crack-` ing of various petroleum oil fractions. t t

3He`retofore, in the art, heating oil blends comprised a relatively large proportion of virgin heating oil constituents as compared to cracked `heatingoil constituents. However, due to the desirability of virgin heating oils as feed stocks to various cracking operations, as for example, a fluid catalytic cracking operation, the blends comprise an increasing proportion of cracked heating oil fractions as compared to virgin stocks. Virgin heating oil fractions are also very desirable as diesel oil products which further decreases their availability for heating oil blends.

slt is known in the art that heating oils consisting com-` pletely or in part of catalytic cracked stocks are characterized by an undesirable instability giving rise` to the formation of sediment." It is also known that when cracked heating oils are blended with conversion sweetened virgin heating oils certain undesirable characteristics are increased due to their incompatibility. As a result, such blended fuel oils tend `to cause clogging of filters, oriiices, or conduits associated with theyburning systems in which they are employed.

It is also known in the art that when asweetened virgin heating oil is blended wtih a cracked heating oil, the carbon residue of the blend in many cases exceeds the carbon residue of either `the virgin heating` oil-or the cracked heating oil. The carbon residue value is obtained by distilling a sample of the product, taking 90% overhead and leaving 10% as bottoms. The bottoms are then subjected to` the standard Conradson'carbon test and the results reported as weight percent of carbon residue on the 10% residual used in the test. This carbon residue is an indication ofthe extent the blendedheating oil will carbonize the burners, particularly a rotary burner" in actual use and to some extent determines theburning chaarcteristics and desirability of the fuel. f In order to improve the quality of blended heating oils, various processes have been practiced in the` art. `Itis known in the art `to process a virginlheating oil by a` t caustic wash if the oil be relatively sweet. On the other hand, if the virgin heating oil has a relatively high mer-, captan content so as to `render it sour, the oil is processed by a doctor treator an ,equivalent` sweeteningloperation.

Heating oil blends which may be processed by the catalytic sweetening Ioperation of the present invention are particularly hydrocarbon mixtures of which more than about 10% preferably from about`l5% to 60% by volume consist of stocks derived from cracking operations, More precisely still, the finished blends may be characterized as petroleum fractions containing a proportion of cracked stocks greater than 10%, preferably from about 15% to 60% by volume, and falling within ASTM specification D-39648T for fuel oils (Grades No. l or 2). Inspections of a typical heating oil blend are for example:

Gravity, API 34.5 Distillation, ASTM:

Initial, B. P., F. 363 10% F. 438 50% C@ F. 504 F. 583 Final, B. P., F. 640 Flash, F. `158 Color, Tag Robinson l5 Viscosity, SSU/ F. 34.7 Pour Point, F. 0 Sulfur, wt. .37 `Suspended Sediment, mgs./ 100 ml. 1.0 Carbon residue on 10% residuum, wt. .08 Corrosion, 1 hr. `@D 212 F. Pass Diesel `index 48.2 Aniline point, F. 140

The process of the present invention may be more fully i understood by reference to the drawing illustrating one embodiment of the same. Referringspecically to the drawing, a crude oil feed stock is introduced into distillation zone l by means of line 2, Temperature and pressure conditions in Zone l. are adapted to remove overhead by means of line 3 normally gaseous hydrocarbons and to remove by means of line i hydrocarbon constituents boiling in the motor fuel and naphtha boiling ranges. A virgin heating oil fraction is removed from zone 1 by means of line 5 while a gas oil fraction is removed by means of line 6. A residuum fraction comprising the higher boiling constituents is removed as. a bottoms by means of line 7. YThe virgin heating oil fraction removed by means of line 5 may be treated by various processes in order to reiine the same. In accordance with the present invention this Virginv heating oil fraction is catalytically sweetened, utilizing a suitable catalyst such as molybdenum oxide on alumina or cobalt or molybdate on alumina.

lt is understood that distillation zone 1 may comprise` any suitable number and arrangement of stages. `The gas .oil fraction remos/,ed` hy. eans ,of line .6 i's passed.

to cracking zone 30 which ,may comprise any suitable `'cracking operation, as for example, a thermal or a catalytic cracking.-v process. However, rthe present invention is-.particularly directed .towardathe production of a high quality virgin-cracked'.l heating oil blend. wherein the cracking process comprises a catalytic operation, as for example, auid'fcatalytic cracking operation.

Ay uid:v catalytic cracking plant is composed of three sections: cracking, regeneration, and fractionation. The cracking `reaction .takes place continuously in one reactor at' a. .temperature in the range from about 800 F. tol 105,0' The spent: catalyst is removed continuously for regeneration in a separate vessel, from which it -i's returned'. .tothe cracking vessel, which is at appressure belowuabout'ZOO 'lbs.,..usual1y below aboutv 50 lbs. per squarewinch. Continuity ofvflow of catalyst, as well as of .oil `is-.thus accomplished,` and the `characteristic features of.uxedbed: designs involving the intermittent shifting `of reactors through cracking, purging, and regenerationncycles..l are eliminated.

Regenerated' catalyst isltwithdrawn from the regenerator and fi'lowsfby/ gravityfdown va standppe, wherein al suiciently high pressure headl is built uponthe catalystto .allow itsinjectionfintotthefresh liquid-oil stream. 'I'heresulting mixture of `oil and catalyst flows into the reaction vessel,..in which gas ivelocity is intentionally low, so;thatahighconcentration of catalyst will result. The cracking. that takes place results in carbon deposition on the catalyst, requiringregeneration ofthe catalyst. The crackedxproduct oil'vapors are withdrawn from the top of the reactor afterpassingthrough cyclone separators to free .them of any -entrained catalyst particles, while the spent catalyst is .withdrawn from the bottom of the reactor ,and` is injected into a stream of undiluted air which carries the catalyst into the regeneration vessel. The products of combustion resulting from the regeneration of the catalyst leave the top of this vessel and pass through a series of cyclones where the bulk of the entrained catalyst is recovered. The regenerated catalyst` is withdrawn from the bottom of the vessel to complete its cycle.

lThe cracked products are removed from cracking zone 30 (overhead from the reactor) by means of line 28and introduced into a distillation zone 16. Temperature and pressure conditions in zone 16 are adjusted to remove overhead by means of line 17 normally gaseous constituents and to remove ,by means of line 18 hydrocarbon constituents boiling in the motor fuel boiling range. A fraction boiling above the heating oil boiling range is removed as a bottoms fraction by means of line 19. Y A fraction boiling in the heating oil boiling range is `removedV by means of line 20 and in accordance with the present invention may be caustic washed in zone-21. The fresh caustic o1' other treating agent is introduced by means of line 22 while the spent-treating agent is removed by .means of line 23. In Aaccordance with the present invention, the caustic washed cracked heating oil is blended with the catalytic sweetened virgin heating oil, produced as hereinafter described.

In accordance with the present invention the virgin heating -oil removed by means of line S is catalytically sweetened in zone 8. vThis operation is carried out-in the presence of a suitable. catalyst such as cobalt molybdate on alumina ormolybdenumtoxide on alumina. In general, the amount of alumina is in the range from about 85 to .95% -byweight lThe'temperatures'utilized in the catalyticallyy sweetened operation are in the range of about 550 to-650 F. Preferredtemperatures are in the rangefrom about 575 to 625 F. Satisfactory pressures are inthe range -from about atmospheric to 40G-p. s. i. g.,while-thepreferred pressures are in the range from about 175 to 250`p. s. i.,g. The-feed rates may vary appreciably depending upon variousselected operating conditions," butin general, are of the order of spacey velccitiesof from about 1 to 16 volumes of feed.

per volume of catalyst per hour. Preferred feed rates are from about 4 to 8 volumes of liquid feed per volume of catalyst per hour.

lIn general, operating conditions are adjusted to secure a. liquid phase operation. Under these conditions less heat transfer equipment is required, since there is no needv to vaporize the feed and condense the product. Furthermore, in a liquid phase operation, carbonaceous materials formed in the reaction zone are continuously washed off the catalyst.

1n, accordance'with one adaptation of the present invention, ,thecatalytically sweetened virgin heating oil fraction l,is withdraw-n from zone `8 by means of line 50 and aftercaustic washing and other treatment for removal of hydrogen sulde is blended with the caustic washed, cracked Iconstituents in vline 24.

While in many instances a satisfactory product can be secureduiilizing asingle stage, that is, a catalytic sweetening stage on the virgin constituents, in many other instancesvinorder tosecure a good yodor product, it is de,- sirable to use a second air vsweetening stage in conjunction with the catalytic `sweetening stage. Under this mode of operationv the catalytic sweetening virgin constituents may b e .passed `through to air caustic sweetened zone v.4,0 by yIneansof line 41. It is more desirable to remove .the catalytic `sweetened stock from zone 8 by means of .line `5,1 and to pass the same to zone 52 wherein hydrogen sulfide is removed. Removal is accomplished preferably lby the introduction of steam by means of line 53, and the removal of hydrogen sulfide by means of line 54.

The, fraction substantially free of hydrogen sultide is removed y,from the bottom of the zone 52 by means of line 5,5l andintroduced into zone 56, wherein the same is contacted with a` Weak caustic solution. caustic solution is introduced into zone 56 by means of line 57 and .withdrawn by means of line 58. This caustic troduced to give good agitation and to provide the necessary oxygen. The time of contact is approximately 15 minutes to 2.40minutes.

I.The catalytic sweetened, caustic-air-sweetened virgin fractionis.k removed from `zone 40 by means of line 42 `and blended with the cracked-constituents introduced by means of line 24.

Thefinventionis 'broadly concerned with the production of a heatingY oil blend comprising cracked and virgin constituents. .In A'accordance with the present process, the virginconstituents-,are catalytically sweetened and are preferably thereafter caustic-air-sweetened prior to blending .with the cracked constituents.

It is of the utmost importance `that the feed stock be be of a particular character, that is, be substantially virgin constituents. If cracked stocks, per se, are utilized, a markedincreasein the carbon residue of the treated oil results. However, the process may be carried out utilizing-acertain-amount of cracked constituents in conjunction with the virgin constituents. Under these cir- `cumstances,.the amount of cracked constituents should not exceed about 251% and should preferably be less than 15% byvolurne, based upon the total feed.

During the course of they operation, carbon tends to accumulate on. thecatalyst. After the etl'ciency of the catalyst hasl decreased. to a predetermined level, the. catalyshmayiberegenerated,by the` removal of .the carbpn, preferably by burning with air.

The weak l The process of the presentinvention may be more fully understood by the following examples illustrating the same: i EXAMPLE 1 A number of operations were carried `outwhereina heating oil having the following specifications Boiling range F-- 307-554 Mercaptan No. 91 Sulfur, weight percent c 0.68 C bon residue (10% residuum) weight percent 0.04

A Mercaptan number is defined asmg. of mercaptan sulfur per 100 inl. of sample. a j i was treated with a catalyst comprising about 10% molybdenum oxide onalumina. The results of these operations are illustrated in the followingtable.

` TABLET rWest Texas light virgin heating oil Column A B C Yes. Yes.

0.57 DNP- Pass. 000,001.. 003,003.

Experimental 0.07,0.08 0.09,0.11. Calculated from Com- 0.05 0.07.

ponente. BlSeidiig Value of Virgin 0.04, 0.06.. 008,012.

1 s v`./hr./v., 600 F., 20o p. s. i. g.

2% 48 Be. caustic, 125 F., required 3 to 4 hours to obtain doctor pass product.

3 50% concentration in cracked heating oil having a carbon residue of 0.10 Wt. percent.

The above results show that although catalytic sweetening reduced the mercaptan number of feed from 91 to 4.5, the product obtained would not pass the doctor test. In other words, it contains some residual mercaptans. However, by giving the catalytically sweetened product a further mild treatment with air and dilute caustic, the mercaptan number was reduced to zero and a doctor pass product was obtained. In obtaining the doctor pass product, there was no marked increase in the value for the carbon residue. i

VJVJHr Feed 1 2 4 6 8 Mercaptan No. mg. S/100 ml 91 2 2 3 4 5 Sulfur, Wt. Percent 0.67 0.44 0. 48 0 51 0. 55 0.55 Carbon Residue, Wt. Percent:

Unblended 0. 07 0.01 0.01 0.01 Blendedl 0.05 0.07 0. E;

EFFECT OF TEMPERATURE AT 200 P. S. I. G. AND 4V./V./HR

Temperature, F Feed 400 500 600 Mercaptan No 91 68 45 2 Sulfur, Wt. Percent. 0. 55 0.50 Carbon Residue W Unblended 0. 04 0. 03 Blended 1 o. o5 o. os

1`Blended in 50-50 proportion with caustic washed cracked heating oil having carbon residue of 0.10 Wt. percent.

From the above it is apparent that the mercaptan num- 5 eration. The carbon residue of lthe product is materially improved.

' EXAMPLE 3 Other operations were conducted to determine the relative effect of sweetening by a hydroiining operation andby a catalytically sweetening operation. The results of these operations are illustrated in Table III.

` TABLE rrr Comparison of hydi'ofining anal` catalytic sweetening of West Texas light virgin heating oil Hydronmg C t1 t a a y 1C B ,-t Catalyst Molyb- Sweetenam? e enum ing Treating Oxide on Alumina Feed Rate, V./V./Hr 8 8 1 Hg Rate, S. C. F. B 1,000 0 0 Pressure, p. s. i. g.- 200 200 200 Temperature, F 600 600 600 Product Inspections: Feed Mercaptan No. mg.S/100 m1 1 4 22 Sulfur, Wt. Percent 0.68 .47 50 0. 60 Carbon Residue, Wt. Percent 0.04 0.01 0.00 0.03

Compatibility with Cracked Heating Oil, Carbon Residue on 50/50 Blend of Treated Virgin and Caustic Washed Cracked Heating Oil 1 0.05 0. 09

l Caustic washed cracked heating oil has carbon residue ci 0.09 wt.

ber decreases as space velocity decreases. It isalso apparent that complete removal of the mercaptans is not obtained even at relatively low space velocities, but that complete removal is secured by subsequent caustic air oppercent. When same cracked oil was blended 50/50 with the West Texas light virgin heating oil sweetened by PbS/S method, carbon residue was 0.42 Wt. percent.

The above results show that although catalytic sweetening gives less sulfur removal than hydroning, the mercaptans as measured by mercaptan number are substantially eliminated. Furthermore, catalytic sweetening gives a substantial reduction in carbon residue and irnproves the compatibility of the sweetened stock with caustic washed cracked heating oil. Catalytic swceten ing has an economical advantage over hydroning in that no hydrogen supply or hydrogen recycle is required. Bauxite treating at 1 v./hr./v. was muc-h less eiective than catalytic sweetening at 8 v./hr./v. in removing mercaptans and in reducing carbon residue.

EXAMPLE Ll A heating oil containing only cracked components boiling in the range of 330 to 650 F. was catalytically sweetened at 600 and 200 lbs. pressure. The carbon residue was increased by this operation from .13 to .46 weight percent, showing that catalytic sweetening is not effective on heating oils containing only cracked constituents. In a second operation a blend containing 80% of light virgin heating oil and 20% of heavy cracked heating oil was catalytically sweetened at 600 F., 200 lbs. pressure, and a feed rate of 4 v./hr./v. Inspections on the feed and product are shown in the following tabulation:

Virgin+ Cat. Sweet- Craeked ened Feed Product Sulfur, Wt. Percent 0. 837 0.717 Mercaptan Number 62 1. 5 Carbon Residue (10%), Wt. Percent 0.01 0. 04

The above results illustrate that when a virgin feed is blended with relatively small amounts of cracked feeds, catalytic sweetening is effective.

What yiS claimed which'comprises contacting .constituents ata ytumperature in the range from ab`0'ut'550"A t' 650"l E {andi at a pressure in the range from about atmospheric'to 400 lbs. p s'. i. g. in theabsence of added gases with a catalyst `selected fromme. `ClMSS C Onsisting-of molybdenum xigiefon alumina and Cobalt ,molyhdaie 0.1.1 alumina and 'hnafte Contacting Sadtteated hydrccarbon c011- stituents with -`calaist-ic and V air-ninfa secondstage; treatment.

2. Process as deiined` by claim 1 wherein` the temperature is in the range from about 575 to 625 F.

3.v Process fon the preparation ofrhigh qualityV heating oil blends comprising cracked` anduvirgin` constituents which comprises contacting said virginl constituents with a catalyst selected from the class of cobalt molybdate on alumina and molybdenum oxide on alumina at a tempcraturein the. ransgrgmahavt 5.50? t0- 550" andE from about atmospheric to;

at"a v'pressure in the range 400 lbs. p. s. i. g., withdrawing lthe virgin constituents from Said Cafalxst au@ bl ,Le ,Same with. cracked constituents "milling, iig. die, ,tuig` il 'boiling fange, whereby a low Conradsol carbon product "is' s'ecur'etyiy 4. Process as. defined .by claiml 3.. wherein` said virgin constituentsf are contacted with` air` and"caustic prior to blending the same with. said` crackedconstituents.

,References 1Citfe'd tile `of this patent UNITED DSTATES PATENTS 

1. IMPROVED PROCESS FOR THE SWEETENING OF HYDROCARBON CONSTITUTENTS BOILING IN THE HEATING OIL BOILING RANGE WHICH COMPRISES CONTACTING SAID CONSTITUENTS AT A TEMPERATURE IN THE RANGE FROM ABOUT 550* TO 650* F., AND AT A PRESSURE IN THE RANGE FROM ABOUT ATMOSPHERIC TO 400 LBS. P S. I. G. IN THE ABSENCE OF ADDED GASES WITH A CATALYST SELECTED FROM THE CLASS CONSISTING OF MOLYBDENUM OXIDE ON ALUMINA AND COBALT MOLYBDATE ON ALUMINA AND THEREAFTER CONTACTING SAID TREATED HYDROCARBON CONSTITUENTS WITH CAUSTIC AND AIR IN A SECOND STAGE TREATMENT. 